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de Castro A, Siedlecki D, Borja D, Uhlhorn S, Parel JM, Manns F, Marcos S. Age-dependent variation of the Gradient Index profile in human crystalline lenses. JOURNAL OF MODERN OPTICS 2011; 58:1781-1787. [PMID: 22865954 PMCID: PMC3408875 DOI: 10.1080/09500340.2011.565888] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
PURPOSE: To reconstruct the gradient index (GRIN) profile of human crystalline lenses ex-vivo using Optical Coherence Tomography (OCT) imaging with an optimization technique and to study the dependence of the GRIN profile with age. METHODS: Cross-sectional images of nine isolated human crystalline lenses with ages ranging from 6 to 72 (post mortem time 1 to 4 days) were obtained using a custom-made OCT system. Lenses were extracted from whole cadaver globes and placed in a measurement chamber filled with preservation medium (DMEM). Lenses were imaged with the anterior surface up and then flipped over and imaged again, to obtain posterior lens surface profiles both undistorted and distorted by the refraction through the anterior crystalline lens and GRIN. The GRIN distribution of the lens was described with three variables by means of power function, with variables being the nucleus and surface index, and a power coefficient that describes the decay of the refractive index from the nucleus to the surface. An optimization method was used to search for the parameters that produced the best match of the distorted posterior surface. RESULTS: The distorted surface was simulated with accuracy around the resolution of the OCT system (under 15 µm). The reconstructed refractive index values ranged from 1.356 to 1.388 for the surface, and from 1.396 to 1.434 for the nucleus. The power coefficient ranged between 3 and 18. The power coefficient increased significantly with age, at a rate of 0.24 per year. CONCLUSION: Optical Coherence Tomography allowed optical, non-invasive measurement of the 2-D gradient index profile of the isolated human crystalline lens ex vivo. The age-dependent variation of the changes is consistent with previous data using magnetic resonance imaging, and the progressive formation of a refractive index plateau.
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Affiliation(s)
- A de Castro
- Instituto de Óptica "Daza de Valdés, Consejo Superior de Investigaciones Científicas, C/ Serrano, 121, Madrid, 28006, Spain
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102
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Furukawa H, Hiro-Oka H, Satoh N, Yoshimura R, Choi D, Nakanishi M, Igarashi A, Ishikawa H, Ohbayashi K, Shimizu K. Full-range imaging of eye accommodation by high-speed long-depth range optical frequency domain imaging. BIOMEDICAL OPTICS EXPRESS 2010; 1:1491-1501. [PMID: 21258564 PMCID: PMC3018118 DOI: 10.1364/boe.1.001491] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 11/18/2010] [Accepted: 11/19/2010] [Indexed: 05/20/2023]
Abstract
We describe a high-speed long-depth range optical frequency domain imaging (OFDI) system employing a long-coherence length tunable source and demonstrate dynamic full-range imaging of the anterior segment of the eye including from the cornea surface to the posterior capsule of the crystalline lens with a depth range of 12 mm without removing complex conjugate image ambiguity. The tunable source spanned from 1260 to 1360 nm with an average output power of 15.8 mW. The fast A-scan rate of 20,000 per second provided dynamic OFDI and dependence of the whole anterior segment change on time following abrupt relaxation from the accommodated to the relaxed status, which was measured for a healthy eye and that with an intraocular lens.
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Affiliation(s)
- Hiroyuki Furukawa
- Center for Natural Science, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0373, Japan
| | - Hideaki Hiro-Oka
- Center for Natural Science, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0373, Japan
| | - Nobuyuki Satoh
- Department of Ophthalmology, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0374, Japan
| | - Reiko Yoshimura
- Center for Natural Science, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0373, Japan
| | - Donghak Choi
- Center for Natural Science, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0373, Japan
| | - Motoi Nakanishi
- Department of Ophthalmology, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0374, Japan
| | - Akihito Igarashi
- Department of Ophthalmology, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0374, Japan
| | - Hitoshi Ishikawa
- School of Allied Health Sciences, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0373, Japan
| | - Kohji Ohbayashi
- Graduate School of Medical Sciences, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 252-0373, Japan
| | - Kimiya Shimizu
- Department of Ophthalmology, Kitasato University, Kitasato 1-15-1, Minamiku, Sagamihara, Kanagawa, 232-0374, Japan
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103
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Hartwig A, Charman WN, Radhakrishnan H. Accommodative response to peripheral stimuli in myopes and emmetropes. Ophthalmic Physiol Opt 2010; 31:91-9. [PMID: 21054470 DOI: 10.1111/j.1475-1313.2010.00796.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE It has been suggested that peripheral refractive error may influence eye growth and the development of axial refractive error, implying that the peripheral retina is sensitive to defocus. This study aimed to evaluate the steady-state accommodative response to peripheral stimuli in 10 young, adult myopes (mean spherical equivalent error -2.10 ± 1.72 D, median -1.63 D, range -0.83 to -6.00 D) and 10 emmetropes (mean spherical equivalent error -0.02 ± 0.35 D, median +0.08 D, range -0.50 to +0.50 D). METHODS The subjects were asked to view monocularly the centre of a screen displaying each of a series of eccentric accommodative targets placed at 5, 10 and 15°. An axial target was viewed for comparison purposes. Accommodation was measured using an open-field autorefractor, each stimulus being varied between about 0 and 4 D with spherical trial lenses placed in front of the viewing eye. RESULTS The results confirm that the peripheral retina is sensitive to optical focus, up to field angles of at least 15°, with accommodative responses weakening as the peripheral angle increases. There is some evidence that peripheral accommodation may be less effective in myopes than emmetropes. CONCLUSIONS Although peripheral accommodation can be demonstrated in the absence of a central stimulus, the accommodation response is normally dominated by the central stimulus and it seems unlikely that peripheral accommodation effects play an important role in refractive development.
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Affiliation(s)
- Andreas Hartwig
- Faculty of Life Sciences, University of Manchester, Manchester, UK
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104
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Burd HJ, Wilde GS, Judge SJ. An improved spinning lens test to determine the stiffness of the human lens. Exp Eye Res 2010; 92:28-39. [PMID: 21040722 PMCID: PMC3384005 DOI: 10.1016/j.exer.2010.10.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 09/10/2010] [Accepted: 10/22/2010] [Indexed: 11/16/2022]
Abstract
It is widely accepted that age-related changes in lens stiffness are significant for the development of presbyopia. However, precise details on the relative importance of age-related changes in the stiffness of the lens, in comparison with other potential mechanisms for the development of presbyopia, have not yet been established. One contributing factor to this uncertainty is the paucity and variability of experimental data on lens stiffness. The available published data generally indicate that stiffness varies spatially within the lens and that stiffness parameters tend to increase with age. However, considerable differences exist between these published data sets, both qualitatively and quantitatively. The current paper describes new and improved methods, based on the spinning lens approach pioneered by Fisher, R.F. (1971) 'The elastic constants of the human lens', Journal of Physiology, 212, 147-180, to make measurements on the stiffness of the human lens. These new procedures have been developed in an attempt to eliminate, or at least substantially reduce, various systematic errors in Fisher's original experiment. An improved test rig has been constructed and a new modelling procedure for determining lens stiffness parameters from observations made during the test has been devised. The experiment involves mounting a human lens on a vertical rotor so that the lens spins on its optical axis (typically at 1000 rpm). An automatic imaging system is used to capture the outline of the lens, while it is rotating, at pre-determined angular orientations. These images are used to quantify the deformations developed in the lens as a consequence of the centripetal forces induced by the rotation. Lens stiffness is inferred using axisymmetric finite element inverse analysis in which a nearly-incompressible neo-Hookean constitutive model is used to represent the mechanics of the lens. A numerical optimisation procedure is used to determine the stiffness parameters that provide a best fit between the finite element model and the experimental data. Sample results are presented for a human lens of age 33 years.
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Affiliation(s)
- H J Burd
- Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
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105
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Ophthalmologic manifestations commonly misdiagnosed as demyelinating events in multiple sclerosis patients. Curr Opin Ophthalmol 2010; 21:436-41. [PMID: 20736835 DOI: 10.1097/icu.0b013e32833eade6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Multiple sclerosis may affect both afferent and efferent visual pathways, and sometimes physicians err on ordinary ophthalmologic diagnosis due to overlapping symptoms between demyelinating and nondemyelinating visual diseases. The present article highlights nondemyelinating ocular occurrences due to physiologic or other pathologic processes that may appear in some patients. RECENT FINDINGS Optic neuritis is representative of the most common and best-studied demyelinating visual occurrence in multiple sclerosis. However, other nondemyelinating visual disturbances also seen in the general population may be erroneously interpreted as being part of the underlying disease. This comparison has not been documented and may be helpful to overcome such difficulties. SUMMARY Based on clinical history and some strategies of ophthalmologic examination, physicians can achieve the correct diagnosis. Some clinical situations, however, may be challenging and a multidisciplinary approach in the care of multiple sclerosis is warranted.
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106
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Hao X, Jeffery JL, Wilkie JS, Meijs GF, Clayton AB, Watling JD, Ho A, Fernandez V, Acosta C, Yamamoto H, Aly MGM, Parel JM, Hughes TC. Functionalised polysiloxanes as injectable, in situ curable accommodating intraocular lenses. Biomaterials 2010; 31:8153-63. [PMID: 20692702 DOI: 10.1016/j.biomaterials.2010.07.065] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 07/15/2010] [Indexed: 10/19/2022]
Abstract
The aged eye's ability to change focus (accommodation) may be restored by replacing the hardened natural lens with a soft gel. Functionalised polysiloxane macromonomers, designed for application as an injectable, in situ curable accommodating intraocular lens (A-IOL), were prepared via a two-step synthesis. Prepolymers were synthesised via ring opening polymerisation (ROP) of octamethylcyclotetrasiloxane (D(4)) and 2,4,6,8-tetramethylcyclotetrasiloxane (D(4)(H)) in toluene using trifluoromethanesulfonic acid (TfOH) as catalyst. Hexaethyldisiloxane (HEDS) was used as the end group to control the molecular weight of the prepolymers, which were then converted to macromonomers by hydrosilylation of the SiH groups with allyl methacrylate (AM) to introduce polymerisable groups. The resulting macromonomers had an injectable consistency and thus, were able to be injected into and refill the empty lens capsular bag. The macromonomers also contained a low ratio of polymerisable groups so that they may be cured on demand, in situ, under irradiation of blue light, in the presence of a photo-initiator, to form a soft polysiloxane gel (an intraocular lens) in the eye. The pre-cure viscosity and post-cure modulus of the polysiloxanes, which are crucial factors for an injectable, in situ curable A-IOL application, were controlled by adjusting the end group and D(4)(H) concentrations, respectively, in the ROP. The macromonomers were fully cured within 5 min under light irradiation, as shown by the rapid change in modulus monitored by photo-rheology. Ex vivo primate lens stretching experiments on an Ex Vivo Accommodation Simulator (EVAS) showed that the polysiloxane gel refilled lenses achieved over 60% of the accommodation amplitude of the natural lens. An in vivo biocompatibility study in rabbits using the lens refilling (Phaco-Ersatz) procedure demonstrated that the soft gels had good biocompatibility with the ocular tissue. The polysiloxane macromonomers meet the targeted optical and mechanical properties of a young natural crystalline lens and show promise as candidate materials for use as injectable, in situ curable A-IOLs for lens refilling procedures.
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Affiliation(s)
- Xiaojuan Hao
- CSIRO Molecular and Health Technologies, Bayview Avenue, Clayton, VIC 3168, Australia.
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107
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Ziebarth NM, Rico F, Moy VT. Structural and Mechanical Mechanisms of Ocular Tissues Probed by AFM. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/978-3-642-03535-7_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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108
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Stachs O, Schumacher S, Hovakimyan M, Fromm M, Heisterkamp A, Lubatschowski H, Guthoff R. Visualization of femtosecond laser pulse–induced microincisions inside crystalline lens tissue. J Cataract Refract Surg 2009; 35:1979-83. [DOI: 10.1016/j.jcrs.2009.06.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 06/18/2009] [Accepted: 06/30/2009] [Indexed: 10/20/2022]
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Ortiz S, Siedlecki D, Remon L, Marcos S. Three-dimensional ray tracing on Delaunay-based reconstructed surfaces. APPLIED OPTICS 2009; 48:3886-3893. [PMID: 19593339 DOI: 10.1364/ao.48.003886] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A method of ray tracing for free-form optical surfaces has been developed. The ray tracing through such surfaces is based on Delaunay triangulation of the discrete data of the surface and is related to finite-element modeling. Some numerical examples of applications to analytical, noisy, and experimental free-form surfaces (in particular, a corneal topography map) are presented. Ray-tracing results (i.e., spot diagram root-mean-square error) with the new method are in agreement with those obtained using a modal fitting of the surface, for sampling densities higher than 40 x 40 elements. The method competes in flexibility, simplicity, and computing times with standard methods for surface fitting and ray tracing.
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Affiliation(s)
- Sergio Ortiz
- Instituto de Optica Daza de Valdés, Consejo Superior de Investigaciones Científicas, C/Serrano 121, 28006 Madrid, Spain.
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110
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Zhou C, Wang J, Jiao S. Dual channel dual focus optical coherence tomography for imaging accommodation of the eye. OPTICS EXPRESS 2009; 17:8947-55. [PMID: 19466144 PMCID: PMC2718716 DOI: 10.1364/oe.17.008947] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
A dual channel dual focus spectral-domain optical coherence tomography was developed for imaging the accommodation of the eye in real time. The system can provide simultaneous cross-sectional imaging of all the surfaces of the anterior segment of the eye including the cornea, anterior chamber, anterior and posterior surfaces of the crystalline lens. Thus, the modification of the curvatures of the anterior and posterior surfaces of the crystalline lens and the dimensions of the anterior segment of the eye with accommodation can be calculated. The system was successfully tested in imaging accommodation. The preliminary results demonstrated the feasibility of this novel approach.
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Affiliation(s)
- Chuanqing Zhou
- Institute for Laser Medicine and Biophotonics, Shanghai Jiao Tong University School of Life Science and Biotechnology, 800 Dongchuan Road, Shanghai 200240, China
| | - Jianhua Wang
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine 1638 NW 10th Ave. Miami, FL 33136, USA
| | - Shuliang Jiao
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine 1638 NW 10th Ave. Miami, FL 33136, USA
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111
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Plainis S, Plevridi E, Pallikaris IG. Comparison of the ocular wavefront aberration between pharmacologically-induced and stimulus-driven accommodation. Ophthalmic Physiol Opt 2009; 29:272-80. [PMID: 19422558 DOI: 10.1111/j.1475-1313.2009.00653.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To compare the ocular wavefront aberration between pharmacologically- and stimulus-driven accommodation in phakic eyes of young subjects. METHODS The aberration structure of the tested eye when accommodating was measured using the Complete Ophthalmic Analysis System (COAS; AMO WaveFront Sciences, Albuquerque, NM, USA). It was used in conjunction with a purposely-modified Badal optometer to allow blur-driven accommodation to be stimulated by a high contrast letter E with a vergence range between +0.84 D and -8.00 D. Pharmacological accommodation was induced with one drop of pilocarpine 4%. Data from six subjects (age range: 23-36 years) with dark irides were collected. RESULTS No correlation was found between the maximal levels of accommodative response achieved with an 8 D blur-driven stimulus and pharmacological stimulation. Pharmacological accommodation varied considerably among subjects: maximum accommodation, achieved within 38-85 min following application of pilocarpine, ranged from 2.7 D to 10.0 D. Furthermore, although the changes of spherical aberration and coma as a function of accommodation were indistinguishable between the two methods for low levels of response, a characteristic break in the pattern of aberration occurred at higher levels of pilocarpine-induced accommodation. This probably resulted from differences in the time course of biometric changes occurring with the two methods. CONCLUSION Measuring the pilocarpine-induced accommodative response at only one time point after its application may lead to misleading results. The considerable inter-individual differences in the time course of drug-induced accommodative response and its magnitude may lead to overestimation or underestimation of the corresponding amplitude of normal, blur-driven accommodation. Stimulating accommodation by topical application of pilocarpine is inappropriate for evaluating the efficacy of 'accommodating' IOLs.
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Affiliation(s)
- S Plainis
- Institute of Vision and Optics, School of Health Sciences, University of Crete, Heraklion, Crete 71003, Greece.
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112
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Jacobs MD. Multiscale systems integration in the eye. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2009; 1:15-27. [DOI: 10.1002/wsbm.29] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Marc D. Jacobs
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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